Sheet resistance is one of the important properties of a sheet material, the precise measurement of which is an important means to assess and monitor a semiconductor material. Meanwhile sheet materials are widely used in the fabrication of electronic components, and the sheet resistance performance thereof directly affects the quality of the component. Sheets of metal materials, alloy materials, and semiconductor materials, and electrically conductive coating materials on a substrate are applied to the semiconductor component fabrication and electronic circuit connection, as well as the surface modification and protection of objects.
The current Chinese National Standard “GB/T 14141-2009 TEST METHOD FOR SHEET RESISTANCE OF SILICON EPITAXIAL, DIFFUSED AND ION-IMPLANTED LAYERS USING A COLLINEAR FOUR-PROBE ARRAY” has made detailed requirements on the four-probe method for testing the sheet resistance of semiconductor materials, that the probe tip should have a hemispherical shape (with a radius of 35 μm-250 μm) or a flat circular section (with a radius of 50 μm-125 μm).
The potential field in the sample generated by the two terminal electrodes in the collinear four-probe array method is unavoidably affected by the two middle testing electrodes. This standard strictly requires that the distance between adjacent probes be 1.59 mm, which limits the application range of the sample. In order to avoid the impact of electric heating of small contact point of probes on the measuring surface, the probe current should be controlled to less than 100 mA. In addition, the shape of the indentation by the probe on the surface of the tested material is difficult to control, and thus repeated testing is required to ensure the reliability of measurement results, as well as to improve the measurement accuracy. In short, the process using the collinear four-probe array method for measuring the sheet resistance of a sheet material is complicated, and demanding on the measurement instruments and operation skills, which limits its application.
For solid electrical insulating materials, the Chinese National Standard “GB/T 1410-2006 METHODS OF TEST FOR VOLUME RESISTIVITY AND SURFACE RESISTIVITY OF SOLID ELECTRICAL INSULATING MATERIALS” specifies the measurement procedures and calculation methods for testing surface resistivity of plate materials using concentric ring electrodes.